Recovery of furfural from furfural-polymer mixtures



Sept. 30,1947.

G. H. MILLER RECOVERY OF FURFURAL FROM FURFURAL-POLYMER MIXTURES Filed May 25, 1945 FURFURAL C HYDROCARBONS SOLV. STORAGE I I I g ,6 FURFURAL I DRY FURFURAI.

WAT E R I EXTRACT ION UNIT INSOL. HYDROCARB'ONS I HYDROCARBON RECOVERY UNIT OLEFINIC HYDROCARBONS CONCENTRATING uni-r 'ADDITIVE rlB I TREATING UNIT POLYMER FURFURAL con-mums IO T0 I57. POLYMER FURFUBAL CONCENTRATING UNIT GORDON H. MILLER INVENTOR BY H ATTO Patented Sept. 30,1947

RECOVERY OF FURFURAL FROM FUR- FURAL-POLYMER} MIXTURES Gordon H. Miller, Port Arthur, Tex, assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application May 25, 1945, Serial No. 595,736

This invention relates to the recovery of furfural from mixtures of furfural and polymer such as produced in the extraction and extractive distillation of hydrocarbon mixtures containing ole-,

fins and di-olefins with furfural.

The invention has to do with the recovery of furfural used in the extraction of olefin containing mixtures wherein the furfural containing dissolved hydrocarbons is subjected to distillation to effect separation between furfural and extracted hydrocarbons, and furfural contaminated with polymer material is treated with water in the presence of a surface-active agent under conditions such as, to effect separation between furfural and the aforesaid polymer material.

Furfural is a useful solvent for effecting fractional separation between olefinic and paraflin hydrocarbons and also for eifecting separation between olefins differing in degree of unsaturation. Thus, it may be used for efiectingseparation between mono-olefins and di-olefins.

It has been found that when furfural is used to extract unsaturates such as butadiene from hydrocarbon mixtures the furfural becomes contaminated during continued use with a small but appreciable amount of polymer or resin material. The mechanism of this polymer formation is not entirely clear. It may be that furfural under the conditions employed during the extractive treatment or during its recovery from the hydrocarbons undergoes polymerization to a small extent, or may enter into reaction with olefinic hydrocarbons forming polymer material, or both of these reactions may take place. Also, the unsaturated hydrocarbons may undergo polymerization in the presence of the furfural.

The presence of this polymer material in the mixture of hydrocarbons and furfural is objectionable because it forms deposits within the plant apparatus and particularly the distillation, heat exchange and other apparatus used for recovering the furfural. It tends to stick to the metal surfaces and as a result during continued exposure to elevated temperatures is converted into solid carbonaceous form. The deposition of this material upon the surfaces of the heat exchangers interferes with their efficient operation and in addition results in the necessity for frequent cleaning of the apparatus. This deposition may be so serious as to cause a shutdown of the plant.

In accordance with the invention wherein it is desired to extract butadiene from a C4 hydrocarbon mixture by extraction or extractive distillation, the hydrocarbon mixture is subjected to contact with furfural at temperatures in the 2 Claims. (Cl. 260347) range of about to 340 F. so as to producean extract phase comprising furfural and dissolved butadiene. This extract phase is separately subjected to distillation, advantageously in the absence of steam, so as to strip the hydrocarbons from the solvent at temperatures in the range about 280 to 340 F. The unvaporized liquid comprises furfural and a small amount of polymer liquid higher boiling than the furfural, andv ranging in amount from a fraction of a per cent to 1 or 2 per cent by weight of the liquid.

This liquid mixture of furfural containing polymer in relatively small proportion is separately subjected to distillation in the absence of steam to remove the bulk of the furfural'in'substantially dry form, leaving a residual fraction comprising furfural and polymer in which the polymer amounts to 10 to 15% by volume, more or less. Thus, itmay contain as much as 50% polymer.

This residual fraction is then treated with a substantial quantity of water under conditions effective to dissolve substantially all of the residual furfural. The aqueous mixture is subjected to settling with gentle agitation in the presence of a small amount of a surface-active agentso that the insoluble polymer material coagulates in a free settling form. The settled polymer is removed from the clear supernatant liquid consistin of furfural dissolved in water. natant liquid is drawn off and subjected to distillation so as to obtain the furfural in substan+ tially dry form or containing only a small amount,

of water.

A feature of the invention thus involves effecting the foregoing settling'in the presence of a small amount of a surface-active agent such as dioctyl ester of sodium sulfosuccinic acid. Addithe peculiar nature of the polymer.

The surface-active agent not only facilitates, this separation but also reduces the tendencyof the polymer material to adhere to the metal surfaces of the treating apparatus and thus facili tates removal of the polymer from the treating".

zone.

t It has been ,found that gentle stirring is essential. If the stirring is too violent during liberation of the polymer, it separate into a finely- The super-j.

I Under ordinary conditions, this separation is difficult to make due to 3 divided form which is difiicult to separate by settling,

The recovered polymer can be used in the man ufacture of plastics.

In actual plant operation, the proportion of this residual fraction or polymer concentrate to the total iurfural employed in thesystem may be relatively small; 'Lherefgre, only a Portion ofthe, recovered solvent may be subjected to the foregoing water extraction step. Thus, 1 or 2% of the total furfural in the system may be continuously withdrawn from the recovery system-intheform of this polymer concentrate and this Withdrawn concentrate is subjected to thewaterextraction to remove furfural in pure form or substantially pure form. The purified furfural is continuously returned to the system. In this Way the accumulation of polymer material in the total solvent is prevented from exceeding a predeter-. mined limit.

For amo o de ai d descr pti n of the n ntion; reierence w ll nowbe made to. the accom, Qanyin drawing wherein the. various stages the process are indicated in, a diagrammatic form,

In, the.drawing-,the, numeral l. refers to an ex-.- tar-active distillation unitwhich may comprise one QEIILQIE stages wherein the C4 hydrocarbon mixture is extracted with turfural. The furfural may be introduced from a source, not shown, through, av conduit 2, while the C4 hydrocarbon feed is introduced from a. source, not shown, through a. conduit 3;

The C4 hydrocarbon feed may comprise a mixure o paraffi s; monoi l n and -o efi s, although itmay comprise either a mixture of oleioaarid porofi ns or a. mix o is d iolefins.

The extraction of butadieneirom the normally gaseous.- mixturecontaining it is usually carried out at temperatures ranging from about 140? F. at the top. of thev tower to about 280, to 340 F. at, the bottom. As. a result, there is obtained, a solutionof'butadiene in iur'fural which is removed through a, conduit. 41. The insoluble hydrocarbons re ining from, the extractive, treatment are discharged t r h a ooo u t I'he solo io oi iu fur l d h ro n passing through, the, conduit is introduced to a hydrocarb n recover n t. w i h o m volve one or more stages, The dissolved hydrocarbons are, stripped, from. he fu-rfural in the absence of steam at a temperature ranging from ahout 280 to 340 F. It is desirable to avoid the use of steam in the distillation so as to maintain the, water content of the furfural; not in excess oi about l.% by Volume. Furiural containing this small amount of, Water efiective as a solvent in the extractive treatment 0f the C4 hydro-carbon feed.

The separated olefins are discharged through a ndui 1 Wh e h furiural from hi h t e ave b en p rated s o du t d t u a o dllit 8., the bulk of the furfural being passed through a pipe 9, to a storage tank [0, While the remainder is. passed to a concentrating unit ll. The furfural passing through pipe ,8 is contamioted ith a sm ll amount of ol m ma or exampl it, may ompr s about 95.6% rural, 3% ate and 1-% pol m r y w i t- About 1 to; 2% oi the total solvent removed through pipe 3 is. passed to the unit H, or an amount suificient to avoid buildup of polymer e solve t. syst m.

I the unit it, the furiural is subjected to disfi lotion in th obsoooo o s am so a too o the bulk of the furfural in substantially dry form which is discharged through a conduit l2. The residual fraction comprises furfural containing about 10 to 15% polymer and may be designated as a polymer concentrate. It is removed through a conduit l3.

This. residual fraction is; conducted to a treating unit l4 wherein it is cornminglleiwith water at a temperature of about F. or in the range about '70 to F. The water is mixed with the polymer concentrate in the proportion of about I0; volumes 015 inthe range from about 8 to 12 volumes of water per volume of concentrate. The proportions of water and the temperature employed; arejsuch; as to effect complete or substantially complete solution of the furi'ural in the water.

Advantageously, the surface active agent is incorporated in the water passing to the unit I4.

Thus, the water is drawn from a source, not s own, throu h. a. ondu t. i. while. he agent mate ial. i likew se drawn rom. s urce; not. own, hrough o oo" i l6 wh ch commune. ot th c nd it to mixture. o w te and. additive y be oio tod; nto condu t 13 h ro sod di o il to o it t.

un t 4. prcvision o ma or. ect v .1 toot o h t od. additive w h he. Po mer n n ra o o d. b se tling wherein pha e. paration oouro atolooott io. oi rosaid tem o a u e, in. tho anse 7 to. .29.? F. a van a eously.

h e in s bjected. to s ni e st rrin Th p me m te ia se le a ioori r oi'o woos. u rol. iss l ed. in rot s pa ates as a. lighter yer. whi h la ter is discharged hrou h a con ui i, he yme b i m v d thr u ondui o. f ri ral so t on co duc ed o. on.- trot ns. u '48 wh re n i is AbJ'ected. QSl P- pi e an a ona distillation, n o e o o e. a es by nven ona mooo 'io order t e: move the water rom ho t r orol the io i being isohoreod th ou h condui 2 Ihis i charged iur oro1. ma co ain a. sma amoun o w e ch. that. wh n re urned to ho solvent o o the Wate oontont o t o to a sol nt n h oxtrooiion ion, o the ystem s man:- tainedat about 4% by volume,

he wa e o ed in he di til tion. stoo ay be i ha d th ough. a ooodo t. 2.2 nd recycled all or i part, r h ooodoi .3 or us in. he. unit l4,

T e surface a i g nt i added t he, water used. n o u i on amount. ran ing. f m about 0 b Wei t oi he wa r- Thus. it is advantageous to mp oy f water so bl or w t isc le oso i- The. a n is. one which roduoos o sori etoo oo o water and reduces he o o o t ns on between po ymer and Water It sh d av a l ostftho ooria o ooti o. p o e e f. so ium noohthooo o. or o aterial c a tha r ou ly men i n d.

S f ce ooo v a ent suitab e or this pur ose. om Wetting os u s'. o somolo of wh h. i lu o al ali meta a s of o lf nio acids; od um ap o ll il; a kal m tal'solts. of acid sul u ic st s o hi h. m oon o we gh a cohol s ch as lauryl sodium suliate; alkyl esters of sodium u fo ooo nio a id such as ho ho r o or the am est r; o the d out l. o to o Sodi m 's lio uooihi ac d and o l o r sulf o tos, 'etc- Co pounds of e ed t the rade u as Na o l. B o osol A r so AY. A r so 1B Aeroso an Ga iool may o so .iitonp l o h t t o r otm ot o the polymer concentrate with water may be effected in a tower employing concurrent flow of polymer concentrate and water containing the additive.

In connection with the foregoing diagram, specific mention has been made of using furfural to extract butadiene from C4 hydrocarbon mixtures. However, it is contemplated that the invention has application to the recovery of furfural from furfural-polymer mixtures resulting in the furfural extraction of other olefinic hydrocarbons or oily materials, as a result of which extraction the furfural becomes contaminated with polymer material.

The invention is thought to have application in the recovery of other solvents of the Furan type, such as furfuryl alcohol and tetrahydrofurfuryl alcohol. Therefore, the term furfural in the appended claims is used in a comprehensive sense to include furfural and its related compounds.

Obviously many modifications and variations of the invention as above set forth may be made without departin from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The method of recovering furfural from a mixture of furfural and polymer which comprises passing to a treating zone a furfural feed containing a substantial amount of polymer formed during contact between furfural and olefinic hydrocarbons at elevated temperatures, subjecting the furfural-polymer mixture therein to contact with a relatively large proportion of water in the presence of a small amount of a water soluble wetting agent effective to coagulate said polymer in free settling form, forming an aqueous phase comprising furfural dissolved in water and an insoluble phase comprising polymer, and separating said phases.

2. The method of recovering furfural'from a mixture of furfural and polymer which comprises passing to a treating zone a furfural feed containing a substantial amount of polymer formed during contact between furfural and olefinic hydrocarbons at elevated temperatures, subjecting the furfural-polymer mixture therein to contact with a relatively large proportion of water in the presence of a small amount of a water soluble wetting agent selected from the class consisting of organic alkali metal sulfates and sulfonates effective to coagulate said polymer in free settling form, forming an aqueous phase comprising furfural dissolved in water and an insoluble phase comprising polymer, and separating said phases.

GORDON H. MILLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,372,668 Hachmuth Apr. 3, 1945 2,372,623 Zinner Mar. 27, 1945 1,980,118 Tyler Nov. 6, 1934 

